Projectile with sting for reducing drag

ABSTRACT

A rearwardly extending axial protuberance, known as a &#39;&#39;&#39;&#39;sting, &#39;&#39;&#39;&#39; is secured to the base of a conventional projectile, such as a bullet or an artillery shell. The sting may assume a variety of configurations, such as cylindrical, frusto-conical, or combinations thereof, and can be utilized as a modification to be added to conventional projectiles, or can be fabricated as an integral part of a new series of projectiles. The sting causes a reduction in base pressure drag and thus lowers the rate of energy loss of the projectile in flight. Such reduction in drag increases the effective range of a bullet by enabling same to maintain a flatter trajectory; a comparable reduction in drag increases the maximum range of an artillery shell.

United States Patent [191 Sieling et a1.

[451 May 7,1974

[ PROJECTILE WITH STING FOR REDUCING DRAG [76] Inventors: Walter R. Sieling, 184 Woodbine Cir., New Providence, NJ. 07974; Norman C. Ziesse, Cora Ln., Box D-8, Chester, NJ. 07930 [22] Filed: Apr. 12, 1972 211 Appl. No.: 243,313

[52] US. Cl. 244/3.3 [51] Int. Cl. F42b 13/02 {58] Field of Search 244/3.233.-3; 102/43, 44, 92.1, 92.4, 3, 2, 52; 42/1 F [56] References Cited UNITED STATES PATENTS 1,817,377 8/1931 James 244/33 X 2,324,346 7/1943 Albree 244/326 X 2,297,130 9/1942 Bomar 244/327 1,806,223 5/1931 Samaia 244/33 X 3,412,962 11/1968 Killian 244/33 X FOREIGN PATENTS OR APPLICATIONS 269.412 4/1927 Great Britain 244/33 10,325 12/1912 Great Britain ..244/3.27

Primary ExaminerVerlin R. Pendegrass Attorney, Agent, or Firm-Eric P. Schellin; Martin P.

Hoffman 5 7 ABSTRACT A rearwardly extending axial protuberance, known as a sting, is secured to the base of a conventional projectile, such as a bullet or an artillery shell. The sting may assume a variety of configurations, such as cylindrical, frusto-conical, or combinations thereof, and can be utilized as a modification to be added to conventional projectiles, or can be fabricated as an integral part of a new series of projectiles. The sting causes a reduction in base pressure drag and thus lowers the rate of energy loss of the projectile in flight.

Such reduction in drag increases the effective range of I a bullet by enabling same to maintain a flatter trajectory; a comparable reduction in drag increases the maximum range of an artillery shell.

10 Claims, 26 Drawing Figures PATENTEHHAY I914 3.809.339

SHEET 1 f 4 Fl 6. mm F/G.Z.

22 (PRIOR ART) MUZZLE VELOCITY= 4480 /sic WITHOUT STING MUZZLE VELOCITY 2240 /SEC IOK WITH sn NG HEIGHT ABOVE GROUND (FEET) WITHOUT STING O IOK 20K K 40K K TANGENT RANGE (FEET) FIELD OF INVENTION The instant invention relates generally to projectiles, and more particularly to projectiles employing axial protuberances known as stings for improving the functional characteristics of such projectiles at velocities in excess of approximately Mach 1.5.

DESCRIPTION OF THE PRIOR ART The total drag of a projectile moving through a fluid medium, such as air, comprises two components, namely, skin drag and base drag. Skin drag is the retarding force created by the friction between the air and the surface of the projectile, the friction being attributable to the formation of a boundary layer of air. Base drag is the retarding force created by the difference in pressure between the front and rear of the projectile. This pressure difference is due to the existence of a low pressure region in the vicinity of the base of the projectile.

Many of the conventional projectiles have attempted to reduce skin drag by sundry forebody configurations and/or surface treatment techniques. While some success in reducing skin drag has been achieved, the concomittant problem of base drag has remained largely unsolved.

A number of efforts have been made in the prior art to minimize base drag. The most common approach is known as the boat-tail and involves tapering the rear section of the projectile along its longitudinal axis. Boat-tails are designed to delay the flow separation process, i.e., to maximize the distance along the projectile that the air flow will follow, or adhere to, the configuration of the projectile body.

Variants of the basic boat-tail have also been evolved. One common variant has utilized a tapered and foreshortened boat-tail; other variants of the boat-tail have relied upon telescoping cylindrical sleeves of decreasing diameter. The telescoping sleeves are disclosed, for example, in U.S. Pat. Nos. 1,817,377, granted to R. W. James and 2,297,130, granted to R. E. Bomar.

Boat-tails" have improved to some extent the operational characteristics of the projectiles employing same. However, all of the variants of the boat-tails are limited in their effectiveness to transonic velocities, i.e., velocities between Mach 0.8 and Mach 1.2 (approximately); at higher speeds, the boat-tails have had minimal impact on improving operational characteristics due to the fact that it is physically impossible for the high speed flow to follow, or adhere to, the boat-tail section of the projectile. Additionally, boat-tails" with telescoping sleeves are unreliable in operation because of their complexity and because of possible changes in both the center of gravity and the center of pressure during flight.

SUMMARY With the shortcomings of the above described conventional projectile configurations clearly in mind, the instant invention proposes axially extending protuberances or stings extending rearwardly from the base of the projectile for the purpose of altering the base region flow and thereby reducing base drag. Furthermore, detailed laboratory tests conducted in wind tunnels under controlled conditions have established l) the veracity of the gas dynamic assumptions upon which the sting was predicated, and (2) the effectiveness of the sting at supersonic speeds. Similar comparative tests have demonstrated the ineffectiveness of boat-tail projectiles at high supersonic speeds and have pointed out fallacies in the theoretical underpinnings of such known configurations. More specifically, the instant invention recognizes that at velocities in excess of Mach 1.5 (approximately 1,500 ft./sec.) the formation of a low pressure at the base region of the projectile is unavoidable, and in many instances, is even desirable for enhancing the stability of the projectile.

A projectile, modified with the addition of an axial protuberance, or sting, can be judiciously designed so that the mass of the modified projectile is identical to the mass of the unmodified projectile, while its range and its effective striking power are materially enhanced at velocities in excess of about Mach 1.5. Calculations based on laboratory test data have established that the effectiveness of the sting increases as the projectile muzzle velocity is stepped up from Mach 1.5 to Mach 4. Theoretical calculations indicate that even more pronounced gains will be realized in excess of Mach 4.

Furthermore, the instant invention contemplates that the stings can be used in conjunction with known boat-tails for projectiles adapted to travel at both subsonic and supersonic speeds. The stings do not impair the operational characteristics of projectiles at subsonic speeds, but only exert a marked salutary ef feet at speeds in excess of approximately Mach 1.5. Additionally, stings can be secured to existing projectiles or can be fabricated as an integral part of a new series of projectiles.

Other advantages of the protuberances, which can be utilized with projectiles of greatly varying size, shape and mass, will become apparent to the skilled artisan from a consideration of the accompanying drawings and the detailed description thereof set forth in the related portions of the specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of the theoretical and actual flows of air over a conventional projectile;

FIG. 2 is a diagrammatic representation of the actual flow of air over a conventional projectile having a boat-tail;

FIG. 3 is a diagrammetic representation of the actual flow of air over a conventional projectile having a modified boat-tail;

FIG. 4 is a diagrammatic representation of the actual flow of air over a projectile having a sting constructed in accordance with the principles of the instant invention;

FIG. 5 is a rear elevational view of the projectile and sting of FIG. 4, such view being taken along line 55 and in the direction indicated;

FIG. 6 is a diagrammatic representation of the flow of air over another projectile constructed in accordance with the principles of the instant invention but employing both a boat-tail and a sting;

FIG. 7 is a rear elevational view of the projectile of FIG. 6 employing both a boat-tail and a sting, such view being taken along line 77 and in the direction indicated;

FIG. 8 is a graph comparing the operational characteristics of an artillery shell with the sting to a conventional artillery shell;

FIGS. 9 and 10 are graphs comparing the operational characteristics of the instant projectile configuration to a conventional projectile;

FIGS. 11 and 12 are graphs comparing the operational characteristics of the improved projectile configuration to a second conventional projectile;

FIGS. 13 and 14 are graphs comparing the operational characteristics of the improved projectile to a third conventional projectile; and

FIGS. 15 and 16 are graphs comparing the operational characteristics of the improved projectile to a fourth conventional projectile.

FIG. 17 is a side elevational view of yet another projectile having a sting constructed in accordance with the principles of the instant invention;

FIG. 18 is a rear elevational view of the projectile and sting of FIG. 17, such view being taken along line 18-18 and in the direction indicated;

FIG. 19 is a side elevational view of yet another projectile constructed in accordance with the principles of the instant invention but employing both a boat-tail" and a sting;

FIG. 20 is a rear elevational view of the projectile of FIG. 19 employing both a boat-tail and a sting, such view being taken along line 20--20 and in the direction indicated;

FIG. 21 is a side elevational view of still another projectile having a sting constructed in accordance with the principles of the instant invention;

FIG. 22 is a rear elevational view of the projectile and sting of FIG. 21, such view being taken along line 2222 and in the direction indicated;

FIG. 23 is a side elevational view of still another projectile constructed in accordance with the principles of the instant invention but employing both a boat-tail and a sting; and

FIG. 24 is a rear elevational view of the projectile of FIG. 23 employing both a boat-tail" and a sting, such view being taken along line 24-24 and in the direction indicated.

FIGS. 25 and 26 illustrate stings having both cylindrical and frusto-conical segments.

DESCRIPTION OF THE INVENTION Referring now in detail to the drawings, FIG. 1 shows a projectile, indicated generally by reference numeral 10, including a leading section 12 which may be rounded, pointed, or flat, an intermediate cylindrical section 14, and a tapered rear section 16 terminating in a point. After projectile 10 has been propelled from a gun barrel not shown), patterns of attached and separated flow are established as the projectile travels towards its destination. In theory, the flow will follow the contour of all sections of the projectile, as indicated by the directional arrows 18, (upper half of FIG. I), with separation occurring at the rear most point of the tapered rear section 16. However, in reality, the fiow will follow the contour of sections 12 and 14, but will separate from the contour of the projectile long before reaching the point of section 16 as indicated by the directional arrows 20, (lower half of FIG. 1 The series of points at which separation occurs is known as the ring of separation, and is identified by reference numeral 22.

Since the area of projectile 10 between the ring of separation 22 and the pointed termination of the rear section 16 serves no useful aerodynamic function, the projectile was foreshortened and the boat-tail projectile 24 was evolved, as depicted in FIG. 2. The boat-tail projectile includes a leading section 26, an intermediate cylindrical section 28, and a tapered, boat-tail section 30. The ring of separation for the air flowing about the projectile occurs near the rear end of boat tail section 30, as indicated by reference numeral 32.

Alternative boat-tail configurations as depicted in FIG. 3 were evolved for increasing the length along the projectile body for which the flow remains attached, i.e., were evolved for delaying the separation process. A representative alternative boat-tail projectile 34 includes a leading section 36, an intermediate cylindrical section 38, and a boat-tail comprising a series of frusto-conical segments 40, 42, 44 and 46. The segments are nested together prior to firing the projectile, but are extended during the subsequent travel to approximate the more widely used boat-tail projectile of FIG. 2. The frusto-conical segments were disclosed in US. Pat. Nos. 1,817,377, granted to R. W. James, and 2,297,130, granted to R. E. Bomar. The ring of separation occurs in the plane identified by reference character 47.

Whereas the projectile configurations of FIG. 1, FIG. 2 and FIG. 3 were satisfactory for reducing base drag for most purposes at transonic speeds, all of the configurations were found to be functionally deficient at supersonic velocities. The deficiencies became even more pronounced as the supersonic velocities were increased above Mach 1.5. Thus, despite the increased capability of weapons of all sizes to launch projectiles with muzzle velocities exceeding the speed of sound, the deficiencies of the projectiles precluded or at least retarded taking full advantage of such increased launching capabilities. To illustrate, as the muzzle velocity was increased, the ring of separation moved forward until it reached the area at which the intermediate and rear sections of the projectile met, thus rendering the boat-tailing ineffective for reducing drag and possibly leading to projectile instabilities.

The instant invention apparently presents the opportunity to blend together advances in ballistics technol' ogy with a comparable advance in projectile design. In accordance with the principles of the instant invention, a projectile identified generally by reference character 48, includes a leading section 50, an intermediate cylindrical section 52, and a rearwardly extending axial protuberance or sting 54. The projectile can be a bullet, or can be an artillery shell. It should be noted that projectiles similar in shape to projectile 48 sans sting 54 and with a flat base as shown are the most commonly used. Directional arrows 56 indicate the path of flow of the air over projectile 48, (top half of FIG. 4). Directional arrows 58 indicate the base pressure on the base of the sting 54, while directional arrows 60 indicate the base pressure on the base of the projectile 48, (lower half of FIG. 4). Separation from the cylindrical section 52 ocours in the plane indicated by numeral 61. In contrast to the known prior art projectile configurations of FIGS. l-3, which sought to eliminate the low pressure region in the near-wake of the projectile, sting 54 increases the total force exerted on the base of the projectile over that which would be experienced in the absence of sting 54. The test proven and theoretical rationale for the advantageous influence of sting 54 is briefly explained by considering a projectile with a zero length sting (a conventional, blunt-based projectile). A certain base pressure is experienced by this projectile during flight. Under identical flight conditions, the presence of sting 54, as shown in FIG. 4, will alter those pressures, indicated by numerals 58 and 60, from the zero length sting case. A knowledgeable selection of the geometrical dimensions of sting 54 will result in an effective increase in base pressure. The corresponding reduction in base drag, which reduces the rate of energy loss in flight for projectile 48, enables bullets utilizing sting 54 to travel a flatter trajectory while increasing its effective range (the range at which projectile 48 maintains adequate energy and accuracy). Additionally, when sting 54 is utilized in conjunction with artillery shells the maximum range of the shell is significantly increased.

FIGS. 6 and 7 illustrate an alternative projectile configuration constructed in accordance with the principles of the instant invention. Such projectile, indicated generally by reference numeral 64, includes a leading section 66, a cylindrical section 68, a tapered boattail" section 70, and a sting 72. Boat-tail section 70 is effective at transonic velocities, and sting 72 is effective at supersonic velocities. Consequently, under those conditions where part of the travel of projectile 64 is at subsonic speeds and part of the travel of projectile 64 is at supersonic speeds, the boat-tail and the sting act consecutively to improve overall performance of the projectile.

A sting, such as sting 54 or 72, can be secured to the base of the projectile simply by drilling a hole in the base of the projectile and forcing the sting into the hole. The mass of the sting is selected to be equal to the mass of the material removed from the projectile so that the total mass of the projectile remains unchanged. If, however, the sting is lighter than the material removed from the projectile, weighting materials can be added to the interior of the projectile in the area of the sting until the total mass reaches the original level. Conversely, if the sting is heavier than the material removed from the projectile, the sting can be partially hollowed without detrimental effects upon performance.

While force-fitting and balancing a sting is suitable for adding a sting to existing projectiles, the sting could also be formed as an integral part of the projectile during its manufacture.

Although FIGS. 4-7 illustrate stings of cylindrical configuration, the stings can assume any number of shapes. For example, the sting can be frusto-conical in shape, (forward or rearward facing) or it can combine both a cylindrical and a frusto-conical segment. Again, the sting, of whatever shape desired, may either be secured to known projectiles in the manner discussed above, or it may be fabricated as an integral part of newly designed projectiles embodying the instant invention.

Laboratory tests in wind tunnels have established that three dimensions are of particular interest in the design of the sting. These dimensions, which are indicated in FIGS. 4-7, are

D diameter of base of the projectile L length of the sting d diameter of the sting With the proper selection of the ratio (L/Dd), the

sting significantly increases the effective base pressure, thereby reducing base drag and increasing substantially the operational characteristics of the projectile. At supersonic speeds, tests have shown that a sting with a diameter of half of the diameter of the base of the projectile will cause an increase in base pressure of about 25 percent, if the ratio shown above is about 0.5. It should be noted that there is a range of the dimensionless variable (L/D-d) for which the same maximum percentage increase in base pressure (25 percent) may be realized. For example; Case I d/D 0.5, 0.35 ZL/( Dd)2 0.7 and Case II d/D 0.333, 0.602 L/(D-d) 2 0.75. These numbers give an indication of the total range of dimensionless parameters for maximum effectiveness. Selection of other dimensionless parameters, i.e., d/D 5 0.166, L/(D-d) E 0.5 would also increase base pressure, but only about 17 percent. The diameter (D) for these laboratory test s has been held constant at 3 inches. Additional tests have demonstrated the sensitivity of the base pressure to sting length (L). The test results were set forth in a paper entitled Influence of Short Base Protuberances on Supersonic Near-Wake Flows delivered to the Canadian Conference on Applied Mechanics in May 1971 at Calgary, Canada.

FIGS. 816 are diverse graphs comparing the predicted operational characteristics of projectiles with stings to conventional projectiles sans stings. The performance curves of FIGS. 8-16 are the results of theoretical calculations based on wind tunnel data and published ballistics tables. The artillery shell data, FIG. 8, emphasizes that the effectiveness of the sting increases as the muzzle velocity increases. The graphs, viewed together, stress that the applicability of a sting, such as sting 54, is not limited by the mass of the projectile, be it 25 grains (as in FIGS. 9 and 10), 50 grains (as in FIGS. 11 and 12), 150 grains (as in FIGS. 13 and 14) or 265 grains (as in FIGS. 15 and 16). The effectiveness of a sting is, moreover, to directly reduce the overall drag coefficient of a projectile.

As previously noted, the stings can assume any number of shapes. To illustrate, a frusto-conical sting 74 extends axially rearwardly from conventional projectile 76 in FIGS. 17 and 18. Sting 74 assumes a forward facing, frusto-conical shape, i.e., the base of the frustum is adjacent to base 78 of projectile 76. FIGS. 19 and 20 depict a forward facing frusto-conical sting 80 that extends axially rearwardly of base 82 of boat-tail 84, which, in turn, extends rearwardly from projectile 86.

FIGS. 21 and 22 depict a frusto-conical sting 88 that is rearwardly facing, i.e., the smallest portion of the frustum is adjacent to base 90 of projectile 92. FIGS. 23 and 24 depict a rearward facing frusto-conical sting 94 that extends axially rearwardly of base 96 of boattail 98, which, in turn, extends rearwardly from projectile 100.

FIG. 25 shows a rear fragment of a projectile with a sting extending longitudinally or axially therebehind; the sting has a cylindrical segment 102 and a frustoconical segment 104. FIG. 26 similarly shows a rear fragment of a projectile with a frusto-conical segment 106 and a cylindrical section 108.

In view of the foregoing description, it will be apparent that modifications to the instant projectile configurations will occur to the artisan versed in the ballistics technology. Consequently, the appended claims should be construed in an illustrative manner consistent with the merits of the technological advance set forth above and should not be restricted to their literal terminology.

We claim:

1. A projectile having improved aerodynamic characteristics at supersonic velocities, said projectile including:

a. a leading section,

b. an intermediate section being substantially cylindrical in shape, and

c. a blunt base extending at substantially a right angle to the longitudinal axis of the leading section and the intermediate section, the improvement consisting of:

l. a sting having a unitary body extending rearwardly from said base of the projectile along the longitudinal axis thereof,

2. said unitary body terminating in a single base extending at substantially a right angle to the longitudinal axis of the projectile and the sting,

3. the maximum diameter of the base of the body of said sting being less than the diameter of the base of said projectile,

4. said sting increasing the average base pressure of the projectile at supersonic velocities.

2. The projectile as defined in claim 1 wherein the body of the sting is cylindrical in shape.

3. The projectile as defined in claim 1 wherein the body of the sting is frusto-conical in shape.

4. The projectile as defined in claim 1 wherein the body of the sting has both cylindrical and frusto-conical segments.

5. An improved projectile including:

a. a leading section,

b. an intermediate section being substantially cylindrical in shape,

0. a tapering boat-tail section for enhancing the aerodynamic characteristics of the projectile at transonic speeds, and

d. a blunt base extending at substantially a right angle to the longitudinal axis of the leading section, the intermediate section and the boat-tail section, the improvement consisting of:

l. a sting having a unitary body extending rearwardly from said base of the projectile along the longitudinal axis thereof,

2. said unitary body terminating in a single base extending at substantially a right angle to the longitudinal axis of the projectile and the sting,

3. the maximum diameter of the base of the body of said sting being less than the diameter of the base of said projectile,

4. said sting increasing the average base pressure of the projectile at supersonic speeds.

6. The projectile as defined in claim 5 wherein the body of the sting is cylindrical in shape.

7. The projectile as defined in claim 5 wherein the body of the sting is frusto-conical in shape.

8. The projectile as defined in claim 5 wherein the body of the sting has both cylindrical and frusto-conical segments.

9. A method of improving the aerodynamic characteristics at supersonic velocities of a projectile including a leading section, an intermediate cylindrical section, and a blunt base extending at a substantially right angle to the longitudinal axis of the leading and intermediate sections, said method including the steps of:

l. drilling a hole in the base,

2. force-fitting one end of a sting with a longitudinally extending body into said hole, and

3. adjusting the mass of the sting to correspond to the mass of the hole so that the total mass of the projectile remains unchanged.

10. A method of improving the aerodynamic characteristics at supersonic velocities of a projectile including a leading section, an intermediate cylindrical section, and a blunt base extending substantially at a right angle to the longitudinal axis of the leading and inter mediate sections, said method comprising the steps of:

the sting is formed thereon. 

1. A projectile having improved aerodynamic characteristics at supersonic velocities, said projectile including: a. a leading section, b. an intermediate section being substantially cylindrical in shape, and c. a blunt base extending at substantially a right angle to the longitudinal axis of the leading section and the intermediate section, the improvement consisting of:
 1. a sting having a unitary body extending rearwardly from said base of the projectile along the longitudinal axis thereof,
 2. said unitary body terminating in a single base extending at substantially a right angle to the longitudinal axis of the projectile and the sting,
 3. the maximum diameter of the base of the body of said sting being less than the diameter of the base of said projectile,
 4. said sting increasing the average base pressure of the projectile at supersonic velocities.
 2. said unitary body terminating in a single base extending at substantially a right angle to the longitudinal axis of the projectile and the sting,
 2. adjusting the total mass of the projectile and the sting so that the total mass of the projectile and sting is the same as the mass of the projectile before the sting is formed thereon.
 2. force-fitting one end of a sting with a longitudinally extending body into said hole, and
 2. said unitary body terminating in a single base extending at substantially a right angle to the longitudinal axis of the projectile and the sting,
 2. The projectile as defined in claim 1 wherein the body of the sting is cylindrical in shape.
 3. The projectile as defined in claim 1 wherein the body of the sting is frusto-conical in shape.
 3. the maximum diameter of the base of the body of said sting being less than the diameter of the base of said projectile,
 3. adjusting the mass of the sting to correspond to the mass of the hole so that the total mass of the projectile remains unchanged.
 3. the maximum diameter of the base of the body of said sting being less than the diameter of the base of said projectile,
 4. said sting increasing the average base pressure of the projectile at supersonic speeds.
 4. The projectile as defined in claim 1 wherein the body of the sting has both cylindrical and frusto-conical segments.
 4. said sting increasing the average base pressure of the projectile at supersonic velocities.
 5. An improved projectile including: a. a leading section, b. an intermediate section being substantially cylindrical in shape, c. a tapering boat-tail section for enhancing the aerodynamic characteristics of the projectile at transonic speeds, and d. a blunt base extending at substantially a right angle to the longitudinal axis of the leading section, the intermediate section and the boat-tail section, the improvement consisting of:
 6. The projectile as defined in claim 5 wherein the body of the sting is cylindrical in shape.
 7. The projectile as defined in claim 5 wherein the body of the sting is frusto-conical in shape.
 8. The projectile as defined in claim 5 wherein the body of the sting has both cylindrical and frusto-conical segments.
 9. A method of improving the aerodynamic characteristics at supersonic velocities of a projectile including a leading section, an intermediate cylindrical section, and a blunt base extending at a substantially right angle to the longitudinal axis of the leading and intermediate sections, said method including the steps of:
 10. A method of improving the aerodynamic characteristics at supersonic velocities of a projectile including a leading section, an intermediate cylindrical section, and a blunt base extending substantially at a right angle to the longitudinal axis of the leading and intermediate sections, said method comprising the steps of: 